Canon EF 400mm f/5.6L USM Accessories

Ideal for press, sports and nature photography, this compact
extender increases the focal length of Canon L-series telephoto or
telephoto zoom lens' by a factor of 1.4x, with higher AF accuracy
and improved communication between camera and lens.

Extender EF 2x III

Ideal for press, sports and nature photography, the extender
increases the focal length of Canon L-series telephoto or telephoto
zoom lens' by a factor of 2x, with higher AF accuracy and improved
communication between camera and lens